San Joaquin-Sacramento Delta

Participants

Gregory B. Pasternack and Kendrick J. Brown

Background

During ~1999-2002 the University of California, Davis Center for Integrated Watershed Science and Management was funded by CALFED to collaborate with the California Department of Water Resources, The Nature Conservancy, and the Seaver Institute to develop a multi-objective restoration planning, design, and monitoring program for the McCormack-Williamson Tract at the northern head of the delta, where the Cosumnes and Mokelumne Rivers join. The MW Tract is a 2.5 square mile delta island that may be the lynchpin to solving the northern delta's flooding and habitat problems given its unique position in the landscape. At one time the island was covered with wetlands, but it was leveed and drained for agriculture at the turn of the century. The elevation of the southern half of the island has dropped since agriculture was initiated. Recently, The Nature Conservancy purchased the island and proposed to create tidal freshwater wetlands on the site by opening levees and allowing water to tidally circulate through it. Before any restoration can take place, extensive basline studies must be conducted.

Purpose

The general objective of the research program on MW Tract was to determine the geomorphic potential of the site to revert back to a functional tidal freshwater marsh with an array of beneficial aquatic and riparian habitats. The geomorphic potential is defined as the elevational, stratigraphic, and sedimentary conditions necessary for a tidal freshwater wetland to exist and function. Based on the work of Hilgartner (1995) and Pasternack (1998), even if intertidal hydrodynamics are restored and plants begin to grow, the long term ecological success of the restoration will depend on watershed-delta interactions that are manifest in the geomorphic conditions.

Methods

The work that was done on the island involved two related but independent projects. The first project tested the utility of shallow seismic reflection technology in reconstructing the island's goemorphic evolution and providing insight for restoration design given revealed stratigraphic layers. This work was funded by the Seaver Institute via a grant to The Nature Conservancy who was our partner in this work. The second project used geomorphic and paleoecological reconstructions from long sediment cores to ascertain the fine scale dyanmics of the delta's evolution in the vicinity of the MW Tract. This work was funded by CALFED. Both projects are completed now.